In the process of laying-up an odd number of veneer sheets to form an assembly of such sheets which are to be glued together thereby to form a plywood panel, each veneer sheet should desirably be provided in a specifically oriented position, e.g. a position in which the sheet is straightened with respect to a given reference direction, for making possible an efficient and accurate laying-up operation. As is known to those skilled in the art, such oriented positioning of veneer sheets in progress is convenient and desirable for ease of handling sheets in processes other than the laying-up process in the manufacture of plywood panels.
A device for controlling the position of a veneer sheet is disclosed by Publication of Examined Japanese Utility Model Application No. 60-30008 (1985) which is assigned to the same assignee as that in the present patent application. This device includes a plurality of feeding rolls for feeding a veneer sheet in a specific direction and a pair of freely rotatable rolls provided at the downstream end of the feeding area with their axes upright and perpendicular to a feeding plane in which the veneer sheet is fed by the feeding rolls and spaced across the feeding direction at an interval which is smaller than the width dimension of a veneer sheet whose inclined position is to be corrected. In such device, if a veneer sheet is fed in a non-straight position with its leading edge inclined with respect to a straight line perpendicular to the feeding direction, the leading edge of such incoming veneer sheet is firstly brought into contact engagement with either one of the two rolls and the veneer sheet is guided laterally by that one roll which is then in rolling contact with the leading edge. Because the veneer sheet is continued to be moved forward by the feeding rolls while being guided laterally, the sheet is caused to be turned until the leading edge is brought into contact engagement with the other roll, where the sheet is straightened with respect to the direction in which it has been fed by the feeding rolls.
In the above device, the two rolls are required to be rotated easily by the rolling contact of the leading edge of the veneer sheet for allowing the sheet to be turned with smoothness. In other words, if the rotational resistance of the rolls is greater than the feeding force imparted to the veneer sheet by the feeder, the rolls cannot be rotated or rolled by the leading edge, so that the sheet may fail to be turned properly and, therefore, to be positioned in the desired straight alignment. Such failure in positioning tends to occur particularly in handling thin veneer sheets whose weight is light and, therefore, the magnitude of the feeding force of which may be too small to cause the rolls to rotate. Under such conditions, the veneer sheet tends to be deformed or bent upwardly without being positioned properly.
Additionally, because each of the freely rotatable rolls in the above device can start rotating only after the leading edge of the veneer sheet has been brought into contact therewith and the roll is thus subjected to the feeding force of the sheet, it takes a relatively long time before the sheet is positioned completely straight.